A. Field of the Invention
The present invention relates generally to the field of medicine. More particularly, it concerns methods of diagnosing and monitoring diseases of the esophagus.
B. Description of Related Art
Making the diagnosis of many inflammatory conditions of the gastrointestinal tract such as severe gastroesophageal reflux (GERD), eosinophilic gastroenteritis (EGE), food allergic enteropathy (FAE), and inflammatory bowel disease (IBD) is often difficult. Serologic and radiographic assessments are not diagnostic for any of these conditions. In the instance of food allergic disorders, skin prick testing and RAST analysis are the only non-invasive tests available. In addition, these tests are beneficial only in identifying IgE mediated reactions and are not useful for cell-mediated reactions. In other instances, non-invasive access to the gastrointestinal (GI) tract is only available through radiographic or stool analysis and again these do not provide definitive diagnostic information for these disorders.
Ultimately, endoscopic analysis is required to obtain mucosal sampling for diagnosis and to develop a treatment plan. Affected tissue sections are characterized by infiltration of polymorphonuclear leukocytes and eosinophils into the diseased sites. For some diseases, such as Crohn's disease, histopathological features are clear and characterized by the finding of chronic ileal inflammation with non-caseating mucosal granulomas. For other diseases, such as eosinophilic gastroenteritis and food allergic disorders, the exact histological features are not as certain and a degree of overlap with other conditions exists.
Methods to study esophageal diseases are limited to in vitro models, a few animal models and human studies of esophageal biopsies. Other, “minimally-invasive” esophageal studies can measure the amount of acid (pH monitor), non-acid (impedance monitor), and bile (Bilitec monitor) in the esophageal lumen. These later tests require placement of an inert probe (approximately 3 mm diameter) through the nose and into the distal esophagus for overnight monitoring. Another test of esophageal inflammation involves swallowing a capsule with a camera that can take pictures of the esophagus. Finally, esophageal function can be measured by placing probes into the esophagus for a pressure and waveform measurements (manometry/motility monitors).
U.S. Pat. No. 6,475,145 discloses a method utilizing a retrievable and ingestible radioactive capsule swallowed by a subject and held in place by means of a cord for diagnosis of GERD and acid-reflux. The radioactive capsule is degraded below pH4 so the measure is a radioactive release. The cord provides a means for retrieving the capsule.
U.S. Pat. No. 5,738,110 describes a device for the diagnosis of certain gastrointestinal pathogens. This device comprises a gelatin capsule which contains a drag material which has thin sample cloth embedded therein, which is attached to a string. The patient holds the string and swallows the capsule, allowing the sample cloth to come into contact with the small intestine. After a period of time, the sampling cloth and the drag material are recovered for testing.
To date, no method has been used to quantify the inflammatory contents of the esophageal lumen. Analogous to bronchial lavage in pulmonary diseases, stool collections in intestinal diseases and urinalysis in renal diseases, measurement of esophageal contents allows a direct definition and measurement of inflammatory mediators associated with esophageal diseases such as GERD and EE. A safe, “minimally invasive” alternative to endoscopy with biopsy to assess esophageal inflammation is therefore needed.